Saturday, June 20, 2020
Friday, June 19, 2020
विचलन रहित वर्ण विक्षेपण
केवल विचलन या केवल विक्षेपण के लिए दो प्रिज्मों (समान्यतः क्राउन तथा फ्लिंट कांच) को संयोजित किया जाता है।
विचलन रहित वर्ण विक्षेपण
माना दो प्रिज्म, एक क्राउन कांच का जिसका प्रिज्म कोण A तथा दूसरा फ्लिंट कांच का जिसका प्रिज्म कोण A' को एक दूसरे के विपरीत अपने आधार को रखते हुए संयोजित करते है।
प्रिज्म - https://vardhmanphysics.blogspot.com/2020/06/blog-post.html
Thursday, June 18, 2020
wave optics
Newton’s Corpuscular Theory
v Newton thought that light
is made up of tinny, light and elastic particles called corpuscles which are emitted by a luminous body.
v The corpuscles travel with
speed equal to the speed of light in all directions in straight lines.
v The corpuscles carry energy
with them. When they strike retina of the eye, they produce sensation of
vision.
v The corpuscles of different
colour are of different size.
v The corpuscles theory
explains that light carry energy and momentum, propagation of light in vacuum and law of Reflection and Refraction.
Reason
Of Failure
v The corpuscular theory
fails to explain interference, diffraction
and polarization.
v A major prediction of
the corpuscular theory is that the speed of light in a denser medium is more
than the speed of light in rarer medium. The truth is that the speed of light
is lesser in rarer medium . Therefore, the Newton’s corpuscular theory is wrong.
Huygen’s Wave Theory
According to this theory
v Light travels in the form
of wave.
v When light waves are
emitted from the source, they travel with uniform velocity in homogeneous medium.
v Different colors are due
to the different wavelengths of light waves.
v When light waves enter our
eyes, we get the sensation of light.
v Light waves are assumed to be
longitudinal type of waves.
For the propagation of light through vacuum, Huygens suggested the existence of
imaginary medium called ether.
Drawbacks
v Huygens assumed the presence of ether everywhere, but experimentally proved that such ether is not present.
v The phenomenon such as photoelectric effect, Compton Effect cannot be explained on the basis of this theory.
v Huygens wave theory cannot explain the phenomenon of polarization of light, because Huygens‟ assumed that light waves are longitudinal waves.
Wavefront
A wavelet is the point of disturbance due to propagation of light.
A wavefront is defined as the continuous locus of those particles of
a medium , which are vibrating in the same phase .
Depending on the shape of the source of light, the wavefront can be
of three types :
1.Spherical Wavefront
2.Cylindrical Wavefront
3.Plane Wavefront
Spherical Wavefront
A wavefront which is originated from a point source of light at
a finite distance.
Cylindrical Wavefront
A wavefront which is originated from a linear source of light at a finite distance.
Plane Wavefront
When the point source or linear source of light is at very large
distance, a small portion of spherical and cylindrical wavefront
appears to be plane , such a wavefront is called a plane wavefront.
Huygens’ Principle of Secondary Wavelets
1. Every point on the given wavefront (called Primary wavefront) acts as a fresh source of new disturbance, called secondary wavelets, which travel in all directions with the velocity of light in the medium.
2. A surface touching these secondary wavelets, tangentially in the forward direction at any instant gives the new wavefront at that instant. This is called secondary wavefront.
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